1 //===-- Common header for PolyEval implementations --------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H 10 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H 11 12 #include "multiply_add.h" 13 #include "src/__support/CPP/type_traits.h" 14 #include "src/__support/common.h" 15 #include "src/__support/macros/config.h" 16 17 // Evaluate polynomial using Horner's Scheme: 18 // With polyeval(x, a_0, a_1, ..., a_n) = a_n * x^n + ... + a_1 * x + a_0, we 19 // evaluated it as: a_0 + x * (a_1 + x * ( ... (a_(n-1) + x * a_n) ... ) ) ). 20 // We will use FMA instructions if available. 21 // Example: to evaluate x^3 + 2*x^2 + 3*x + 4, call 22 // polyeval( x, 4.0, 3.0, 2.0, 1.0 ) 23 24 namespace LIBC_NAMESPACE_DECL { 25 namespace fputil { 26 27 template <typename T> 28 LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T> 29 polyeval(const T &, const T &a0) { 30 return a0; 31 } 32 33 template <typename T> 34 LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> polyeval(T, 35 T a0) { 36 return a0; 37 } 38 39 template <typename T, typename... Ts> 40 LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T> 41 polyeval(const T &x, const T &a0, const Ts &...a) { 42 return multiply_add(x, polyeval(x, a...), a0); 43 } 44 45 template <typename T, typename... Ts> 46 LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> 47 polyeval(T x, T a0, Ts... a) { 48 return multiply_add(x, polyeval(x, a...), a0); 49 } 50 51 } // namespace fputil 52 } // namespace LIBC_NAMESPACE_DECL 53 54 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H 55